1. Field of the Invention
This invention relates to a recording and/or reproducing apparatus of a rotary head type.
2. Description of the Prior Art
FIG. 1 illustrates a prior art tape format of an 8 mm video tape recorder, in which reference numeral 2 designates a magnetic tape, 3 a magnetic track, 4T a tape running direction upon recording, and 4H a head tracing direction.
The length of the track 3 is made to correspond to 216.degree. of a rotational angle of a rotary magnetic head, in which an audio signal is recorded on a segment 3A of 36.degree. from the beginning of the track, and while a video signal is recorded on a segment 3V of the remaining 180.degree..
In this case, however, the audio signal recorded on the segment 3A is converted to a PCM signal and the time base thereof is compressed so that one field thereof is positioned in this segment 3A. The video signal on the segment 3V is the signal at every field period. In this case, the luminance signal thereof is converted to an FM signal, while a carrier chrominance signal is low frequency converted. They are interleaved with respect to each other at every odd and even period.
Furthermore, the tracks 3 are adjoining to one another, and every other track and the every other remaining track are arranged to have a different so-called azimuth angle. On and throughout the whole length of the track 3, there is superimposed and recorded a pilot signal that is used in tracking servo operation upon playback.
In an actual 8 mm video tape recorder, the PCM signal is time-compressed to about 1/6 times and is recorded on an interval of about 30.degree. at substantially the center of the segment 3A, while the remaining intervals before and after the same are assigned to guard segments. In the present application, for simplicity, it is assumed that the length of this segment 3A is selected to be 36.degree. and the PCM audio signal is recorded over the full length thereof of
Accordingly, a rotary magnetic head assembly used in the 8 mm video tape recorder is constructed as shown in FIG. 2.
In the figure, reference numerals 1A and 1B designate a pair of rotary magnetic heads. These heads are mounted on a rotary drum 5 with an angular spacing of 180.degree. maintained therebetween and are rotated at a frame frequency of a video signal in the head tracing direction 4H. A tape 2 is wrapped slantwise around the rotation circumferential surface of the heads 1A and 1B over an angular range of a little larger than 216.degree. and is transported in the predetermined direction 4T.
For the above mentioned tape format, instead of the video signal, an audio signal is recorded on the video segment 3V.
That is, as shown in FIG. 3, the segment 3V is equally divided by 5 at every angle of 36.degree.. Accordingly, the track 3 is divided into a total of 6 segments .circle.1 to .circle.6 along the lengthwise direction. In the first recording, of the segments .circle.1 to .circle.6 only the segment .circle.1 for example, is used at every track 3 to record the audio signal, and in the second recording, for example, only the segment .circle.2 is used at every track 3 to record the audio signal. In other words, of the segments .circle.1 to .circle.6 , only one segment is used at every track 3 to record the audio signal.
At that time, the audio signal is recorded with the signal format exactly the same as the signal format of the PCM signal recorded on the segment 3A shown in FIG. 1. Furthermore, the segments .circle.1 to .circle.6 can be used freely regardless of the sequential order.
Accordingly, the same tape 2 can be freely used as a video tape or as an audio tape, and when the tape is used only as the audio tape, the recording time can be increased 6 times the recording time when the tape is used as the video tape. See published Japanese Patent No. 57-15287, corresponding to published European Application No. 85,578, incorporated herein by reference.
The audio signal on the audio segment 3A or on the divided segments .circle.1 to .circle.6 are recorded in the form of a PCM signal. Furthermore, the tape 2 is housed in a tape cassette and the tape cassette is of a small size. Accordingly, a tape recorder for the exclusive use of the audio signal can be realized by using the segment 3A, or the segments .circle.1 to .circle.6 in which case the tape recorder can be used as a headphone stereo player such as the so-called WALKMAN (registered trademark).
In the 8 mm video tape recorder, however, the diameter of one pair of magnetic heads of the rotary drum 5 is standardized to be 40 mm so that if the headphone stereo player is constructed with heads which are the same as the video player, it becomes large in size and heavy in weight.